Lab Grown Diamond Depth and Table Percentage: What the Numbers Mean

When reviewing a lab grown diamond certificate, two numbers stand out beyond the 4Cs: depth percentage and table percentage. These proportions are fundamental to how your diamond handles light, directly determining its brilliance, fire, and scintillation.

What Is Table Percentage?

The table is the large, flat facet on top of a diamond — the window through which you look into the stone. Table percentage expresses the table's width as a percentage of the diamond's total width (girdle diameter).

Formula: Table % = Table Width ÷ Average Girdle Diameter × 100

What Table Percentage Does

• Too large (>63%) — lets too much light exit through the top, reducing fire (spectral colors). The diamond appears bright but "lifeless" without rainbow flashes.
• Too small (<53%) — reduces brilliance because not enough light enters through the top. May create dark areas when viewed face-up.
• Ideal range (54-60%) — balances brilliance (white light return) with fire (spectral dispersion), creating the most beautiful visual effect.

What Is Depth Percentage?

Depth percentage measures the diamond's total height (from table to culet) as a percentage of its width.

Formula: Depth % = Total Depth ÷ Average Girdle Diameter × 100

What Depth Percentage Does

• Too deep (>63%) — light enters through the crown but leaks out the sides or bottom instead of reflecting back to your eye. The diamond appears dark in the center.
• Too shallow (<57%) — light passes straight through the bottom without reflecting. The diamond may show a "fisheye" effect — a visible reflection of the girdle through the table.
• Ideal range (59-62.5%) — light enters through the table, bounces off the pavilion facets at the correct angles, and reflects back through the crown to your eye. Maximum brilliance.

Ideal Proportions by Diamond Shape

Round Brilliant

Parameter	Excellent	Very Good	Good
Table %	54-57%	52-58%	50-63%
Depth %	59-62.3%	58-63%	56.5-65%
Crown Angle	34-35°	32-36°	30.5-37.5°
Pavilion Angle	40.6-41°	40.2-41.4°	39.6-42°

Princess Cut

Parameter	Ideal Range
Table %	67-72%
Depth %	64-75%

Oval Cut

Parameter	Ideal Range
Table %	53-63%
Depth %	58-62%
L/W Ratio	1.35-1.50

Emerald Cut

Parameter	Ideal Range
Table %	61-69%
Depth %	61-67%
L/W Ratio	1.30-1.50

Cushion Cut

Parameter	Ideal Range
Table %	56-62%
Depth %	61-68%
L/W Ratio	1.00-1.10 (square) or 1.15-1.25 (rectangular)

Pear Shape

Parameter	Ideal Range
Table %	53-63%
Depth %	58-62%
L/W Ratio	1.50-1.75

Marquise Cut

Parameter	Ideal Range
Table %	53-63%
Depth %	58-62%
L/W Ratio	1.75-2.25

The Relationship Between Depth and Table

Depth and table percentages are interconnected. A diamond with a larger table generally has a shallower crown (the angled portion above the girdle), which affects depth percentage. Understanding this relationship helps explain why:

• A 62% depth with a 55% table behaves differently than 62% depth with a 62% table
• Crown angle and pavilion angle (which contribute to depth) matter as much as total depth
• The overall cut grade integrates all proportions into a single quality assessment

How to Read These Numbers on a Certificate

On your lab grown diamond's grading report, look for:

• Measurements section — lists exact dimensions in millimeters
• Proportions diagram — a visual representation showing table %, depth %, crown angle, pavilion angle, girdle thickness, and culet size
• Cut grade — the overall assessment that integrates all proportions (for round brilliants only — fancy shapes don't receive cut grades from most labs)

Practical Buying Tips

For Round Brilliants

Stick to the Excellent/Ideal cut grade range. If the lab has given the stone an Excellent cut, the proportions have been evaluated holistically and deemed optimal. The specific numbers matter less than the final grade.

For Fancy Shapes

Since fancy shapes don't receive standardized cut grades from most labs, understanding depth and table becomes more important. Use the ideal ranges listed above as guidelines, but also look at the stone's appearance — proportions that produce beauty in practice matter more than numbers on paper.

Face-Up Size

A diamond with a shallower depth (within acceptable ranges) will appear larger when viewed from above — its weight is spread across a wider face rather than hidden in depth. This is especially valuable when comparing apparent sizes between different stones of the same carat weight.

Common Proportion Mistakes to Avoid

• "Spread" diamonds — very shallow stones that look large face-up but sacrifice light performance. If depth is below 57% for a round, be cautious.
• "Nail head" diamonds — deep stones where the table appears dark because light leaks through the bottom. Depth above 63% for rounds is a warning sign.
• Ignoring crown/pavilion angles — total depth alone doesn't tell the full story. Two diamonds with 61% depth can perform very differently based on where that depth is distributed.

Recommended Pieces

• Ladies Ring 2.00Ct Round/Oval/Pear 14K Whi
• Ladies Tennis Necklace 85.00Ct Round 14K Yellow Gold
• 14K White Gold 4 1/2Ct Round/Marquise/Emerald Ladies Ring

Every diamond in our collection is selected for optimal proportions that maximize beauty and light performance.